Processes

Editorial

Jump to: Research, Review

4 pages, 184 KiB

Open AccessEditorial

Special Issue on “Advanced Combustion and Combustion Diagnostic Techniques”

by Zhihua Wang

Processes 2023, 11(4), 1174; https://doi.org/10.3390/pr11041174 - 11 Apr 2023

Viewed by 933

Abstract

Our world still greatly relies on the combustion process to convert fuel into power and heat for purposes such as gas turbines, internal combustion (IC) engines, jet engines, rockets, boilers, and furnaces [...] Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

Research

Jump to: Editorial, Review

20 pages, 11177 KiB

Open AccessArticle

Gas Flow and Ablation of 122 mm Supersonic Rocket Nozzle Investigated by Conjugate Heat Transfer Analysis

by Jatuporn Thongsri, Kamonwan Srathonghuam and Adulyasak Boonpan

Processes 2022, 10(9), 1823; https://doi.org/10.3390/pr10091823 - 9 Sep 2022

Cited by 11 | Viewed by 3709

Abstract

The propellant gas flow of a supersonic rocket in inappropriate operating conditions can cause excessive ablation inside a nozzle. In this research, conjugate heat transfer analysis (CHTA), consisting of computational fluid dynamics (CFD) and finite element analysis (FEA), was applied to investigate the [...] Read more.

The propellant gas flow of a supersonic rocket in inappropriate operating conditions can cause excessive ablation inside a nozzle. In this research, conjugate heat transfer analysis (CHTA), consisting of computational fluid dynamics (CFD) and finite element analysis (FEA), was applied to investigate the gas flow and ablation of a 122 mm nozzle as a case study in the transient state, based on actual operating conditions. First, the nozzle was tested in a static experiment. Then, the experimental results were employed for CHTA settings and validation. Next, after completing the CFD calculation, the results revealed that the nozzle’s gas flow, temperature, pressure, Mach number, shock, etc. were consistent with theoretical results. Finally, using the CFD results as loads, the FEA results showed the equivalent von Mises stress (σ_v), which was consistent with the ablation results from the experiment, as expected. The more the σ_v, the greater the ablation. Both σ_v and ablation were high near the throat and decreased further away. In addition, increasing the insulators’ thickness reduced σ_v, leading to ablation reduction. The research findings contribute to an understanding of ablation and the methodology of employing CHTA to improve the design of 122 mm and other nozzles with reduced ablation for higher efficacy. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

15 pages, 5708 KiB

Open AccessArticle

Combustion Regime Identification in Turbulent Non-Premixed Flames with Principal Component Analysis, Clustering and Back-Propagation Neural Network

by Hanlin Zhang, Hao Lu, Fan Xie, Tianshun Ma and Xiang Qian

Processes 2022, 10(8), 1653; https://doi.org/10.3390/pr10081653 - 20 Aug 2022

Cited by 6 | Viewed by 2063

Abstract

Identifying combustion regimes is important for understanding combustion phenomena and the structure of flames. This study proposes a combustion regime identification (CRI) method based on rotated principal component analysis (PCA), clustering analysis and the back-propagation neural network (BPNN) method. The methodology is tested [...] Read more.

Identifying combustion regimes is important for understanding combustion phenomena and the structure of flames. This study proposes a combustion regime identification (CRI) method based on rotated principal component analysis (PCA), clustering analysis and the back-propagation neural network (BPNN) method. The methodology is tested with large-eddy simulation (LES) data of two turbulent non-premixed flames. The rotated PCA computes the principal components of instantaneous multivariate data obtained in LES, including temperature, and mass fractions of chemical species. The frame front results detected using the clustering analysis do not rely on any threshold, indicating the quantitative characteristic given by the unsupervised machine learning provides a perspective towards objective and reliable CRI. The training and the subsequent application of the BPNN rely on the clustering results. Five combustion regimes, including environmental air region, co-flow region, combustion zone, preheat zone and fuel stream are well detected by the BPNN, with an accuracy of more than 98% using 5 scalars as input data. Results showed the computational cost of the trained supervised machine learning was low, and the accuracy was quite satisfactory. For instance, even using the combined data of CH4-T, the method could achieve an accuracy of more than 95% for the entire flame. The methodology is a practical method to identify combustion regime, and can provide support for further analysis of the flame characteristics, e.g., flame lift-off height, flame thickness, etc. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

18 pages, 4479 KiB

Open AccessArticle

Effects of Methanol Application on Carbon Emissions and Pollutant Emissions Using a Passenger Vehicle

by Zhao Zhang, Mingsheng Wen, Yanqing Cui, Zhenyang Ming, Tongjin Wang, Chuanqi Zhang, Jeffrey Dankwa Ampah, Chao Jin, Haozhong Huang and Haifeng Liu

Processes 2022, 10(3), 525; https://doi.org/10.3390/pr10030525 - 7 Mar 2022

Cited by 38 | Viewed by 5765

Abstract

Methanol, as a promising carbon-neutral fuel, has become a research hotspot worldwide. In this study, pure gasoline and gasoline blended with five different volume ratios of methanol (10%, 20%, 30%, 50%, and 75%) were selected as test fuels, which were referred to as [...] Read more.

Methanol, as a promising carbon-neutral fuel, has become a research hotspot worldwide. In this study, pure gasoline and gasoline blended with five different volume ratios of methanol (10%, 20%, 30%, 50%, and 75%) were selected as test fuels, which were referred to as M0, M10, M20, M30, M50, and M75. The experiments on carbon and pollutant emissions and performance were carried out on a passenger vehicle with gasoline direct injection (GDI) turbocharged engine using the steady-state, new European driving cycle (NEDC), and acceleration approaches. The results show that under steady-state conditions, as the methanol blending ratio increases, the volume of fuel consumption increases. Compared with pure gasoline, the equivalent fuel consumption and the CO₂ emissions are reduced by 0.95 L/100 km (10.6%) and 18.95 g/km (9.6%) in maximum extent by fueling M75, respectively. In the NEDC, the CO₂ emissions of M30 are reduced by 5.46 g/km (3.7%) compared with pure gasoline. After blending methanol in gasoline, CO emissions increase, and the emissions of NO_x, THC, and PM decrease. The acceleration time is shortened with the increase of blending ratio of methanol. The application of methanol reduces the combustion CO₂ emissions by 10% and improves the pollutant emissions. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

15 pages, 9658 KiB

Open AccessArticle

The Prediction of Spark-Ignition Engine Performance and Emissions Based on the SVR Algorithm

by Yu Zhang, Qifan Wang, Xiaofei Chen, Yuchao Yan, Ruomiao Yang, Zhentao Liu and Jiahong Fu

Processes 2022, 10(2), 312; https://doi.org/10.3390/pr10020312 - 5 Feb 2022

Cited by 20 | Viewed by 2957

Abstract

Engine development needs to reduce costs and time. As the current main development methods, 1D simulation has the limitations of low accuracy, and 3D simulation is a long, time-consuming task. Therefore, this study aims to verify the applicability of the machine learning (ML) [...] Read more.

Engine development needs to reduce costs and time. As the current main development methods, 1D simulation has the limitations of low accuracy, and 3D simulation is a long, time-consuming task. Therefore, this study aims to verify the applicability of the machine learning (ML) method in the prediction of engine efficiency and emission performance. The support vector regression (SVR) algorithm was chosen for this paper. By the selection of kernel functions and hyperparameters sets, the relationship between the operation parameters of a spark-ignition (SI) engine and its economic and emissions characteristics was established. The trained SVR algorithm can predict fuel consumption rate, unburned hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) emissions. The determination coefficient (R²) of experimental measured data and model predictions was close to 1, and the root-mean-squared error (RMSE) is close to zero. Additionally, the SVR model captured the corresponding trend of the engine with the input, though some existed small errors. In conclusion, these results indicated that the SVR model was suitable for the applications studied in this research. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

20 pages, 54246 KiB

Open AccessArticle

An Artificial Neural Network Model to Predict Efficiency and Emissions of a Gasoline Engine

by Ruomiao Yang, Yuchao Yan, Xiaoxia Sun, Qifan Wang, Yu Zhang, Jiahong Fu and Zhentao Liu

Processes 2022, 10(2), 204; https://doi.org/10.3390/pr10020204 - 21 Jan 2022

Cited by 23 | Viewed by 4899

Abstract

With global warming, and internal combustion engine emissions as the main global non-industrial emissions, how to further optimize the power performance and emissions of internal combustion engines (ICEs) has become a top priority. Since the internal combustion engine is a complex nonlinear system, [...] Read more.

With global warming, and internal combustion engine emissions as the main global non-industrial emissions, how to further optimize the power performance and emissions of internal combustion engines (ICEs) has become a top priority. Since the internal combustion engine is a complex nonlinear system, it is often difficult to optimize engine performance from a certain factor of the internal combustion engine, and the various parameters of the internal combustion engine are coupled with each other and affect each other. Moreover, traditional experimental methods including 3D simulation or bench testing are very time consuming or expensive, which largely affects the development of engines and the speed of product updates. Machine learning algorithms are currently receiving a lot of attention in various fields, including the internal combustion engine field. In this study, an artificial neural network (ANN) model was built to predict three types of indicators (power, emissions, and combustion phasing) together, including 50% combustion crank angle (CA50), carbon monoxide (CO), unburned hydrocarbons (UHC), nitrogen oxides (NOx), indicated mean effective pressure (IMEP), and indicated thermal efficiency (ITE). The goal of this work was to verify that only one machine learning model can combine power, emissions, and phase metrics together for prediction. The predicted results showed that all coefficients of determination (R²) were larger than 0.97 with a relatively small RMSE, indicating that it is possible to build a predictive model with three types of parameters (power, emissions, phase) as outputs based on only one ANN model. Most importantly, when optimizing the powertrain control strategy of a hybrid vehicle, only a surrogate model can help establish the relationship between the input and output parameters of the whole engine, which is the need of the future research. Overall, this study demonstrated that it is feasible to integrate three types of combustion-related parameters in a single machine learning model. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

13 pages, 13623 KiB

Open AccessFeature PaperArticle

Laminar Burning Velocity of Lean Methane/Air Flames under Pulsed Microwave Irradiation

by Elna J. K. Nilsson, Tomas Hurtig, Andreas Ehn and Christer Fureby

Processes 2021, 9(11), 2076; https://doi.org/10.3390/pr9112076 - 19 Nov 2021

Cited by 2 | Viewed by 1662

Abstract

Laminar burning velocity of lean methane/air flames exposed to pulsed microwave irradiation is determined experimentally as part of an effort to accurately quantify the enhancement resulting from exposure of the flame to pulsed microwaves. The experimental setup consists of a heat flux burner [...] Read more.

Laminar burning velocity of lean methane/air flames exposed to pulsed microwave irradiation is determined experimentally as part of an effort to accurately quantify the enhancement resulting from exposure of the flame to pulsed microwaves. The experimental setup consists of a heat flux burner mounted in a microwave cavity, where the microwave has an average power of up to 250 W at an E-field in the range of 350–380 kV/m. Laminar burning velocities for the investigated methane/air flames increase from 1.8 to 12.7% when exposed to microwaves. The magnitude of the enhancement is dependent on pulse sequence (duration and frequency) and the strength of the electric field. From the investigated pulse sequences, and at a constant E-field and average power, the largest effect on the flame is obtained for the longest pulse, namely 50 μs. The results presented in this work are, to the knowledge of the authors, the first direct determination of laminar burning velocity on a laminar stretch-free flame exposed to pulsed microwaves. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

11 pages, 3555 KiB

Open AccessFeature PaperArticle

Simultaneous Quantitative Detection of HCN and C₂H₂ in Combustion Environment Using TDLAS

by Wubin Weng, Marcus Aldén and Zhongshan Li

Processes 2021, 9(11), 2033; https://doi.org/10.3390/pr9112033 - 14 Nov 2021

Cited by 13 | Viewed by 2508

Abstract

Emission of nitrogen oxides (NO_x) and soot particles during the combustion of biomass fuels and municipal solid waste is a major environmental issue. Hydrogen cyanide (HCN) and acetylene (C₂H₂) are important precursors of NO_x and soot [...] Read more.

Emission of nitrogen oxides (NO_x) and soot particles during the combustion of biomass fuels and municipal solid waste is a major environmental issue. Hydrogen cyanide (HCN) and acetylene (C₂H₂) are important precursors of NO_x and soot particles, respectively. In the current work, infrared tunable diode laser absorption spectroscopy (IR-TDLAS), as a non-intrusive in situ technique, was applied to quantitatively measure HCN and C₂H₂ in a combustion environment. The P(11e) line of the first overtone vibrational band v₁ of HCN at 6484.78 cm⁻¹ and the P(27e) line of the v₁ + v₃ combination band of C₂H₂ at 6484.03 cm⁻¹ were selected. However, the infrared absorption of the ubiquitous water vapor in the combustion environment brings great uncertainty to the measurement. To obtain accurate temperature-dependent water spectra between 6483.8 and 6485.8 cm⁻¹, a homogenous hot gas environment with controllable temperatures varying from 1100 to 1950 K provided by a laminar flame was employed to perform systematic IR-TDLAS measurements. By fitting the obtained water spectra, water interference to the HCN and C₂H₂ measurement was sufficiently mitigated and the concentrations of HCN and C₂H₂ were obtained. The technique was applied to simultaneously measure the temporally resolved release of HCN and C₂H₂ over burning nylon 66 strips in a hot oxidizing environment of 1790 K. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

13 pages, 3150 KiB

Open AccessFeature PaperArticle

Equivalence Ratio Measurements in CH₄/Air Gases Based on the Spatial Distribution of the Emission Intensity of Femtosecond Laser-Induced Filament

by Ming Li, Jiangpeng Gu, Dayuan Zhang, Qiang Gao and Bo Li

Processes 2021, 9(11), 2022; https://doi.org/10.3390/pr9112022 - 12 Nov 2021

Cited by 2 | Viewed by 1993

Abstract

Femtosecond lasers have been used in combustion diagnostics. Based on the characteristics of femtosecond laser filamentation, many diagnostic techniques have been developed. Here, we propose a method, based on femtosecond laser filamentation, for equivalence ratio measurements in CH₄/air gases. By measuring [...] Read more.

Femtosecond lasers have been used in combustion diagnostics. Based on the characteristics of femtosecond laser filamentation, many diagnostic techniques have been developed. Here, we propose a method, based on femtosecond laser filamentation, for equivalence ratio measurements in CH₄/air gases. By measuring the spatially resolved spectra of the femtosecond laser-induced filament, we found that the variation of the equivalence ratio in the flow field would affect the spatial distribution of the emission intensity of femtosecond laser-induced filament. On this basis, the equivalence ratio was calibrated by using the relative spatial positions of N₂ (337 nm) and C₂ (516.5 nm) signals in the filament. This method overcomes the interference of local air disturbance, having lower measurement uncertainty. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

17 pages, 7806 KiB

Open AccessArticle

Investigation of Hydrogen Content and Dilution Effect on Syngas/Air Premixed Turbulent Flame Using OH Planar Laser-Induced Fluorescence

by Li Yang, Wubin Weng, Yanqun Zhu, Yong He, Zhihua Wang and Zhongshan Li

Processes 2021, 9(11), 1894; https://doi.org/10.3390/pr9111894 - 23 Oct 2021

Cited by 5 | Viewed by 1995

Abstract

Syngas produced by gasification, which contains a high hydrogen content, has significant potential. The variation in the hydrogen content and dilution combustion are effective means to improve the steady combustion of syngas and reduce NO_x emissions. OH planar laser-induced fluorescence technology (OH-PLIF) [...] Read more.

Syngas produced by gasification, which contains a high hydrogen content, has significant potential. The variation in the hydrogen content and dilution combustion are effective means to improve the steady combustion of syngas and reduce NO_x emissions. OH planar laser-induced fluorescence technology (OH-PLIF) was applied in the present investigation of the turbulence of a premixed flame of syngas with varied compositions of H₂/CO. The flame front structure and turbulent flame velocities of syngas with varied compositions and turbulent intensities were analyzed and calculated. Results showed that the trend in the turbulent flame speed with different hydrogen proportions and dilutions was similar to that of the laminar flame speed of the corresponding syngas. A higher hydrogen proportion induced a higher turbulent flame speed, higher OH concentration, and a smaller flame. Dilution had the opposite effect. Increasing the Reynolds number also increased the turbulent flame speed and OH concentration. In addition, the effect of the turbulence on the combustion of syngas was independent of the composition of syngas after the analysis of the ratio between the turbulent flame speed and the corresponding laminar flame speed, for the turbulent flames under low turbulent intensity. These research results provide a theoretical basis for the practical application of syngas with a complex composition in gas turbine power generation. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

13 pages, 4636 KiB

Open AccessArticle

Investigation of Thermal Radiation from Soot Particles and Gases in Oxy-Combustion Counter-Flow Flames

by Chaoyang Wang, Guangtong Tang, Huibo Yan, Lujiang Li, Xiaopei Yan, Zhicong Li and Chun Lou

Processes 2021, 9(10), 1756; https://doi.org/10.3390/pr9101756 - 30 Sep 2021

Cited by 2 | Viewed by 1900

Abstract

Oxy-combustion with high flame temperature, low heat loss, high combustion efficiency, and low NOx emissions is being extensively studied. The thermal radiation from soot particles and gases in oxy-combustion accounts for the vast majority of the total heat transfer. Based on a detailed [...] Read more.

Oxy-combustion with high flame temperature, low heat loss, high combustion efficiency, and low NOx emissions is being extensively studied. The thermal radiation from soot particles and gases in oxy-combustion accounts for the vast majority of the total heat transfer. Based on a detailed chemical reaction mechanism coupled with the soot particle dynamics model and optically thin radiation model, the influence of the flame structure and temperature distribution on the thermal radiation in oxygen-enriched counterflow diffusion flames was studied in this paper. The results revealed that reasonable assignment of total recycled flue gas and the degree of dilution of fuel and oxidant were critical, which can be used to adjust the overall radiation situation of the flame. At the same adiabatic flame temperature, as the fuel concentration decreased and the oxidant concentration increased (the stoichiometric mixture ratio is from 0.3 to 0.6), the soot formation decreased, which led to the particle radiation disappearing while the main radiation zone of gases moved 0.04 cm toward the fuel side. At the same stoichiometric mixture fraction (0.4), the radiation area was broadened and the radiation of soot particles was gradually enhanced with the adiabatic flame increasing from 2300 K to 2700 K. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

19 pages, 5415 KiB

Open AccessArticle

Influence of Porous Media Aperture Arrangement on CH₄/Air Combustion Characteristics in Micro Combustor

by Fei Wang, Xueming Li, Shuai Feng and Yunfei Yan

Processes 2021, 9(10), 1747; https://doi.org/10.3390/pr9101747 - 29 Sep 2021

Cited by 5 | Viewed by 2362

Abstract

Micro-electro-mechanical systems (MEMS) occupy an important position in the national economy and military fields, and have attracted great attention from a large number of scholars. As an important part of the micro-electromechanical system, the micro-combustor has serious heat loss due to its small [...] Read more.

Micro-electro-mechanical systems (MEMS) occupy an important position in the national economy and military fields, and have attracted great attention from a large number of scholars. As an important part of the micro-electromechanical system, the micro-combustor has serious heat loss due to its small size, unstable combustion and low combustion efficiency. Aiming at enhancing the heat transfer of the micro-combustor, improving the combustion stability and high-efficiency combustion, this paper embedded porous media in the combustor, and the effects of different parameters on the combustion characteristics were numerically studied. The research results showed that the layout of porous media should be reasonable, and the small and large pore porous media embedded in the inner and outer layers, respectively, can bring better combustion performance. Meanwhile, A: 10–30 has a high and uniform temperature distribution, and its methane conversion rate reached 97.4%. However, the diameter ratio of the inner layer to the outer layer (d/D) of the porous medium should be maintained at 0.4–0.6, which brings a longer gas residence time, and further enables the pre-mixed gas to preheat and burn completely. At a d/D of 0.5, the combustor has the highest outer wall temperature and CH₄ conversion efficiency. Besides, compared with the pore size increasing rate of Δn = 10 PPI and Δn = 10 PPI, the radial temperature distribution of the Δn = 10 PPI combustor is more uniform, meanwhile avoids the occurrence of local high temperature. Under the condition of Δn = 10 PPI, A: 20–30 layout maintains excellent thermal and combustion performance. In addition, the lean flammable limits of MC-U20, MC-10/30-0.8, and MC-20/30-0.5 were compared, at an inlet velocity of 0.5 m/s, the corresponding lean flammable limits are 0.5, 0.4, and 0.3, respectively, among them MC-20/30-0.5 has a wider flammable limit range, showing excellent combustion stability. This research has guiding significance for the combustion stability of the micro combustor. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

15 pages, 3737 KiB

Open AccessFeature PaperArticle

Numerical Study on the Characteristics of Methane Hedging Combustion in a Heat Cycle Porous Media Burner

by Fei Wang, Xueming Li, Shuai Feng and Yunfei Yan

Processes 2021, 9(10), 1733; https://doi.org/10.3390/pr9101733 - 28 Sep 2021

Cited by 3 | Viewed by 1705

Abstract

With the rapid development of portable devices and micro-small sensors, the demand for small-scale power supplies and high-energy-density energy supply systems is increasing. Comparing with the current popular lithium batteries, micro-scale burners based on micro-thermal photoelectric systems have features of high power density [...] Read more.

With the rapid development of portable devices and micro-small sensors, the demand for small-scale power supplies and high-energy-density energy supply systems is increasing. Comparing with the current popular lithium batteries, micro-scale burners based on micro-thermal photoelectric systems have features of high power density and high energy density, the micro-scale burner is the most critical part of the micro-thermal photovoltaic system. In this paper, the combustor was designed as a heat cycle structure and filled with porous media to improve the combustion characteristics of the micro combustor. In addition, the influence of the porous media distribution on the burner center temperature and wall temperature distribution were studied through numerical simulation. Furthermore, the temperature distribution of the combustor was studied by changing the porous media parameters and the wall parameters. The research results show that the heat cycle structure can reduce heat loss and improve combustion efficiency. When the combustion chamber is filled with porous media, it makes the radial center temperature rise by about 50 K and the temperature distribution more uniform. When filling the heat cycle channel with porous media the wall temperature can be increased. Finally, the study also found that as methane is combusted in the combustor, the temperature of the outer wall gradually increases as the intake air velocity increases. The results of this study provide a theoretical and practical basis for the further design of high-efficiency combustion micro-scale burners in the future. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

16 pages, 5790 KiB

Open AccessArticle

Combustion of Laser-Induced Individual Magnesium Microparticles under Natural Convection

by Chengyuan Lin, Minqi Zhang, Yue Wang, Shengji Li, Xuefeng Huang, Jiangrong Xu and Sunqiang Pan

Processes 2021, 9(8), 1276; https://doi.org/10.3390/pr9081276 - 24 Jul 2021

Cited by 6 | Viewed by 2395

Abstract

Metal magnesium (Mg) fuels have been widely used in rocket propellants. The combustion study on individual Mg microparticles is crucial to the in-depth unveiling of the combustion mechanism of Mg-based propellants. In this paper, a new experimental setup was proposed to directly observe [...] Read more.

Metal magnesium (Mg) fuels have been widely used in rocket propellants. The combustion study on individual Mg microparticles is crucial to the in-depth unveiling of the combustion mechanism of Mg-based propellants. In this paper, a new experimental setup was proposed to directly observe the combustion of individual micron-sized Mg particles, based on laser ignition and microscopic high-speed cinematography. The combustion process of individual Mg microparticles could be directly and clearly observed by the apparatus at high temporal and spatial resolutions. Individual Mg microparticles took gas phase combustion, and mainly underwent four stages: expansion, melting, gasification, ignition, and combustion. The ignition delay time and total combustion time had an exponential decay on the particle diameter, and they had a linear decay on the ignition power density. The melting took a dominant role in the whole burnout time. The gas-phase combustion flame seemed thick, inhomogeneous, and ring-like structure. The combustion model of individual Mg microparticles was built through combining the experimental results with the SEM, XRD, XPS, and EDS analysis of original samples and combustion residues. This study will be beneficial to understand the combustion process and reveal the combustion mechanism of metal microparticles besides Mg. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

12 pages, 2832 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Interactive Effects in Two-Droplets Combustion of RP-3 Kerosene under Sub-Atmospheric Pressure

by Hongtao Zhang, Zhihua Wang, Yong He, Jie Huang and Kefa Cen

Processes 2021, 9(7), 1229; https://doi.org/10.3390/pr9071229 - 16 Jul 2021

Cited by 9 | Viewed by 2547

Abstract

To improve our understanding of the interactive effects in combustion of binary multicomponent fuel droplets at sub-atmospheric pressure, combustion experiments were conducted on two fibre-supported RP-3 kerosene droplets at pressures from 0.2 to 1.0 bar. The burning life of the interactive droplets was [...] Read more.

To improve our understanding of the interactive effects in combustion of binary multicomponent fuel droplets at sub-atmospheric pressure, combustion experiments were conducted on two fibre-supported RP-3 kerosene droplets at pressures from 0.2 to 1.0 bar. The burning life of the interactive droplets was recorded by a high-speed camera and a mirrorless camera. The results showed that the flame propagation time from burning droplet to unburned droplet was proportional to the normalised spacing distance between droplets and the ambient pressure. Meanwhile, the maximum normalised spacing distance from which the left droplet can be ignited has been investigated under different ambient pressure. The burning rate was evaluated and found to have the same trend as the single droplet combustion, which decreased with the reduction in the pressure. For every experiment, the interactive coefficient was less than one owing to the oxygen competition, except for the experiment at L/D₀ = 2.5 and P = 1.0 bar. During the interactive combustion, puffing and microexplosion were found to have a significant impact on secondary atomization, ignition and extinction. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

16 pages, 20577 KiB

Open AccessArticle

A Theoretical Study on the Thermodynamic Cycle of Concept Engine with Miller Cycle

by Jungmo Oh, Kichol Noh and Changhee Lee

Processes 2021, 9(6), 1051; https://doi.org/10.3390/pr9061051 - 16 Jun 2021

Cited by 9 | Viewed by 5444

Abstract

The Atkinson cycle, where expansion ratio is higher than the compression ratio, is one of the methods used to improve thermal efficiency of engines. Miller improved the Atkinson cycle by controlling the intake- or exhaust-valve closing timing, a technique which is called the [...] Read more.

The Atkinson cycle, where expansion ratio is higher than the compression ratio, is one of the methods used to improve thermal efficiency of engines. Miller improved the Atkinson cycle by controlling the intake- or exhaust-valve closing timing, a technique which is called the Miller cycle. The Otto–Miller cycle can improve thermal efficiency and reduce NOx emission by reducing compression work; however, it must compensate for the compression pressure and maintain the intake air mass through an effective compression ratio or turbocharge. Hence, we performed thermodynamic cycle analysis with changes in the intake-valve closing timing for the Otto–Miller cycle and evaluated the engine performance and Miller timing through the resulting problems and solutions. When only the compression ratio was compensated, the theoretical thermal efficiency of the Otto–Miller cycle improved by approximately 18.8% compared to that of the Otto cycle. In terms of thermal efficiency, it is more advantageous to compensate only the compression ratio; however, when considering the output of the engine, it is advantageous to also compensate the boost pressure to maintain the intake air mass flow rate. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

Review

Jump to: Editorial, Research

40 pages, 10912 KiB

Open AccessFeature PaperReview

Review of Development and Comparison of Surface Thermometry Methods in Combustion Environments: Principles, Current State of the Art, and Applications

by Siyu Liu, Yu Huang, Yong He, Yanqun Zhu and Zhihua Wang

Processes 2022, 10(12), 2528; https://doi.org/10.3390/pr10122528 - 28 Nov 2022

Cited by 5 | Viewed by 3360

Abstract

Temperature is one of the most important parameters in the combustion processes. Accurate surface temperature can help to gain insight into the combustion characteristics of various solid or liquid fuels, as well as to evaluate the operating status of combustion power facilities such [...] Read more.

Temperature is one of the most important parameters in the combustion processes. Accurate surface temperature can help to gain insight into the combustion characteristics of various solid or liquid fuels, as well as to evaluate the operating status of combustion power facilities such as internal combustion engines and gas turbines. This paper mainly summarizes and compares the main surface thermometry techniques, from the aspects of their principles, current state of development, and specific applications. These techniques are divided into two categories: contact-based thermometry and non-intrusive thermometry. In contact-based thermometry, conventional thermocouples as well as thin-film thermocouples are introduced. These methods have been developed for a long time and are simple and economical. However, such methods have disadvantages such as interference to flow and temperature field and poor dynamic performance. Furthermore, this paper reviews the latest non-intrusive thermometry methods, which have gained more interest in recent years, including radiation thermometry, laser-induced phosphorescence, liquid crystal thermography, the temperature-sensitive paint technique, and the temperature-indicating paint technique. Among them, we highlighted radiation thermometry, which has the widest measurement ranges and is easy to acquire results with spatial resolution, as well as laser-induced phosphorescence thermometry, which is not interfered with by the emissivity and surrounding environment, and has the advantages of fast response, high sensitivity, and small errors. Particularly, laser-induced phosphoresce has attracted a great deal of attention, as it gets rid of the influence of emissivity. In recent years, it has been widely used in the thermometry of various combustion devices and fuels. At the end of this paper, the research progress of the above-mentioned laser-induced phosphorescence and other techniques in recent years for the surface thermometry of various solid or liquid fuels is summarized, as well as applications of combustion facilities such as internal combustion engines, gas turbines, and aero engines, which reveal the great development potential of laser-induced phosphorescence technology in the field of surface thermometry. Full article

(This article belongs to the Special Issue Advanced Combustion and Combustion Diagnostic Techniques)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Advanced Combustion and Combustion Diagnostic Techniques

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (17 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI